The present invention relates to a process for hydrogenating polymers derived from olefin units having 4 carbon atoms and thereby preparing products which are colorless, odorless, stable to heat and storage and which fulfill the requirements for white oils and medicinal oils.
White oils usually are mineral oils which are prepared by high purification of petroleum fractions boiling in the lubricating oil boiling range. This process usually comprises two steps: a desulfurization followed by hydrogenation under very severe operating conditions. White oils are allowed to be used in or in contact with food, only if they fulfill the official requirements for foodstuffs. The most widely applied standards are the official requirements in the U.S. regulations promulgated by the FDA, the German regulations set forth in DAB VII and the British regulations set forth in the B.P. acid test.
It has already been proposed to purify polymers which are prepared from olefin units having 4 carbon atoms, particularly polybutenes by means of a hydrogenation process, in order to obtain a colorless and substantially odorless polybutene which can be used, for example, as a substitute for natural squalane in cosmetic formulas. However, the product obtained does not come close to fulfilling the white oils requirements. Indeed, the iodine value of the hydrogenated product, which characterizes the unsaturation degree of the product, is much too high.
U.S. Pat. No. 3,100,808 teaches the hydrogenation of polybutene at a temperature of between 60.degree. and 350.degree. C, at a pressure of between 3.5 and 210 kg/cm.sup.2 in the presence of nickel, palladium or platinum on an alumina support, but the iodine value of the hydrogenated product is higher than 1. Such an iodine value is absolutely too high in order for the hydrogenated product to fulfill the while oils requirements.